Consistency responsive device



Sept. 15, 1964 E. J. TRIMBEY CONSISTENCY RESPONSIVE DEVICE 5 sheets-sh'et 1 Filed June 30, 1961 HHHHHHH uvmvrox EDWARD J. TRIMBEY Ell! AT TOR NE'Y.

Sept. 15, 1964 E. J. TRIMBEY CONSISTENCYRESPONSIVE DEVICE 5 Sheets-Sheet 2 Filed June (50, 1961 INVENTOR. EDWARD J. TRIMBEY ATTORNY.

Sept. 15, 1964 E. J. TRIMBEY 3,148,533

CONSISTENCY RESPONSIVE DEVICE Filed June 50. 1961 5 Sheets-Sheet 3 INVEN TOR. EDWARD J. TRIMBEY BY Qgwzzf@ AT TOQNE Y.

Sept. 15, 1964 E. J. TRIMBEY 3,148,533

CONSISTENCY RESPONSIVE DEVICE Filed June 30, 1961 5 Sheets-Sheet 4 ET| I INVENTOR.

B EDWARD J. TRIMBEY ATTORNEY.

Sept. 15, 1964 E. J. TRIMBEY 3,148,533

- CONSISTENCY RESPONSIVE DEVICE Filed June so, 1961 s Sheets-Sheet s INVENTOR. EDWARD J. TRIMBEY ATTORNEY.

United States Patent 3,148,533 CONSISTENCY RESPONSIVE DEVICE Edward J. Trimhey, 19 W. Notre Dame, Glens Falls, N.Y. Filed June 30, 1961, Ser. No. 121,096 2 Claims. (Cl. 73-59) This invention relates to new and useful improvements in a method of and structural refinements in an apparatus for regulating the consistency of a suspended solution and broadly envisions an apparatus for and process of automatically controlling the consistency, on a continuous basis, of a fluent material, consisting of an admixture of solid matter and a freely flowing liquid, in a closed pipe line or in an open area such as a stuff box or other compartments through which pulp may be flowing.

The invention will be specifically illustrated in connection with its use in automatically regulating the consistency of paper stock or other fibrous pulps, although it is to be understood that the invention is not to be restricted to such specific purpose, as it comprehends use in any analogous art where there is a continuous flow of a fluid to be regulated.

In paper manufacture, the pulp or other stock, in an aqueous suspension, is pumped from a beater chest to the Jordans or other refining engines and therefrom to the stuff box of the paper making machine or is pumped to other chests or to pulp metering devices. For various practical reasons, it is important to know and to regulate the consistency of the stock at any of these several stages.

In known prior art, various consistency regulators have operated on a principle of a change in torque caused by the rotating of an element disposed in the pulp according to any variance in its consistency. Such rotatable elements have comprised paddle arms or broad blades or cylinders or balls or cones or discs rotating on top of a flowing stream of pulp. The torque created by such a rotating element has been opposed by means of a compressible spring or equivalent suitable counteracting de-. vice. However, in such devices, the total of the torque created has necessitated employment of a spring means of such great strength or stiffness that it is insensitive to minute changes set up in the torque, as for example, changes of a few hundredths of a percent of consistency. Resultant operations, accordingly, do not give as close or sensitive a consistency control as is demanded for optimum results in current practices.

The invention hereof resides in the particular arrangement, construction and relationship of the various elements in a consistency regulator for use with fluent materials, consisting of solids in a liquid, by which an economical, simple and quick-responding means for controlling consistency is provided, permitting straight line flow, eliminating piping offsets, and avoiding a necessity for special fittings or piping.

The invention broadly comprehends means which are responsive to the consistency of the fluent material employed therewith, such as pulp or stock for use in the making of paper or similar fibrous products, and it may be stated that it is one of the primary objects hereof to provide a regulatory system comprising the steps of and means for maintaining a consistency in the characteristics of the fluent material by a responsive device which gives an accurate and immediate response to variations in the consistency of the fluent material, which accuracy is unaffected by volumetric or pressure changes, and which effectuates the operation of control means for maintaining any desired or predetermined constant condition.

Another salient object of the invention is to provide a mechanical arrangement which will deliver a predetermined rate of fiber to the papermaking machine and will eifect a constant Weight of papermaking material per unit volume of stock as delivered to said paperrnaking machine.

Other prime objects of my invention include; first, the securement of a higher degree of accuracy in the manner of work performed therewith than has heretofore been possible with prior devices known in the art; second, the attainment of a flexibility or a capability of adjustment by which a large variety of work can be produced by means of the same device; third, the provision of a construction which may be readily installed with respect to the various locations where it may be installed; and fourth, the provision of such other improvements in and relating to consistency indicators and regulators of the type above referred to as are hereinafter described and claimed.

It is known that when moving elements of considerable cross sectional area are placed in the path of the pulp flow, changes in the rate of flow exert varying shear values for the same consistency of pulp. The salient improvements claimed herefor make use of the basic principle of the change in the shear force required to move a rotating member through a mass of pulp, as the concentration of fibers or the consistency of the mass is varied, I having determined that a greater portion of the torque created by a rotating disc may be balanced against the moment of rotation caused by the free mountings of a motor having a vertically-disposed axis, and that simultaneously, a smaller portion of the torque created may be balanced against a counteracting force such as a spring means, all so as to permit the employment of a light spring means having a capacity for reacting to the small changes in the value of the portion of the torque created and as induced by minute changes in the consistency of the material being regulated.

Another significant improvement hereof lies in the minimization, if not the complete elimination, of such changes in torque as are caused by changes in the velocity of the mass of the fluent material passing through the regulator body due to variations in the volume or quantity at which the fluent material is being transferred or used, which changes in torque are not desired as intelligence for the purposes of my system and/ or structure inasmuch as such changes normally have no effect upon the factors involved in consistency regulation.

In the cases of the above-referred-to prior art systems, the rotating paddle arms or blades or cylindrical members or spherical or conical elements, as the case may be, are placed in the direct path of the moving fluent material being regulated, with the entire shear reaction being balanced against a spring so as to necessitate the use of a spring of such stiffness as to balance the entire force developed, as aforesaid. As a consequence, minute differences in shear caused by changes, such as in the order of A or of 1%, are not detectable. Given a fixed velocity of rotation of said rotating element, and further, given a certain velocity of movement of the mass of said fluent material, there is a resultant relative velocity of movement between the rotating element and the fluent material. Should the velocity of movement of the fluent material change, a corresponding change in the relative velocity of movement between the rotating element and the fluent material ensues to effectuate a change in the de veloped torque, even though the consistency of the fluent material may remain the same.

As will be observed in the detailed specification which follows, by the system and means hereof, the entire flow of the fluent material being regulated is passed from a source of supply through a pump and then through the regulator of the invention. Changes in the consistency of the fluent material, as it passes through said regulator, effectuate operation of a dilution valve at the pump to accomplish a variance in the quantity of the dilution Water admitted to the suction side of the pump for mix- Patented Sept. 15, 1964 3% ing with the mass of the fluent material wherefor, moments therefollowing, the modified material, having been effected by the change in dilution, is discharged into said regulator in manner to further control the operation of its instrumentalities, all so as to maintain the material at a continuously even density or consistency.

The invention is not to be considered as limited in its application to the specific details of construction and arrangement of parts, as are illustrated in these drawings, since it is capable of other embodiments. Changes and alterations are contemplated and such other embodiments may be utilized within the scope of the claims, without departing from the basic principles and the contemplated scope hereof.

All of the above itemized and other objects and advantages of the invention will become apparent as the description proceeds. Said invention comprises the features hereinafter fully described and particularly pointed out in the following description and annexed drawings setting forth in detail a certain illustrative embodiment thereof, it being indicative, however, of but one of the various ways in which the principles of the invention may be employed.

In said annexed drawings:

FIG. 1 is a more or less diagrammatic view showing the apparatus of the invention in front elevation;

FIG. 2 is a side elevational view taken from the right of the apparatus as shown in FIG. 1;

FIG. 3 is a top plan view of the apparatus shown in FIG. 1;

FIG. 4 is a diagrammatic representation of the components shown in FIG. 1 and illustrating the balance of forces in the apparatus, with certain components being shown in phantom for purposes of clarity; and

FIG. 5 is a diagrammatic representation illustrating a typical installation of the consistency regulator of the invention.

In the following description and claims, various details will be identified by specific names for convenience. These names, however, are intended to be as generic in their application as the art will permit.

A vertically-disposed rotatable thin disc is positioned centrally within a regulator housing or body 12 and intermediate vertically-aligned entrance and exit openings 16 and 18 respectively, through which the mass of the fluent material flows into and out of said regulator housing.

The invention comprehends a flat, smooth annular disc 10 which will be without serrations, blades or warped surfaces and which will be protected from the direct impingement of the moving stream of the fluent material, as will subsequently be seen, so that changes in the rate of flow will have no effect on its accuracy of operation.

The main body or chamber portion of the regulator body 12 will be observed to be cylindrical in shape at its midsection and to have an enlarged cross section preferably but not obligatorily approximately ten times as large as the cross section of the conduit carrying the fluent material to said regulator body. Such expansion in chamber diameter etfectuates a reduction in the velocity of movement in the area where the disc 10 is positioned to something in the area of one half foot per second where the linear velocity of the periphery of an 18 diameter disc, when running at 100 r.p.m., is about 8' per second, all wherefor any change in relative velocity between the fluent material and disc 10, caused by any moderate change in the material velocity in the supply line, is comparatively slight.

The upper and lower portions of regulator body 12 are substantially cone-shaped, the cones extending in oppositely-facing directions, as shown.

Said disc 10 is carried at the inner end of a horizontally-disposed output shaft 20 of a motor reducer 22, which shaft inner end is extendable through a packing gland 24 seated in a wall of regulatory body 12 so as to project into the regulator body chamber sutficiently to dispose the disc at the mid-section of said chamber.

The disc 10 may be secured to the extremity of shaft 20, as by a bolt 28 or other suitable means.

The significant point, is that the plane of the disc is on the axis of flow of the fluent material through the regulator body whereas the axis of the shaft 20 driving said disc is horizontally disposed at right angles to said plane.

Externally of the regulator body, said output shaft 20 is carried in a pair of ball-bearing pillow blocks 30 mounted upon a suitably supported bracket 32.

Said output shaft 20 is driven by a gear reducer motor 40, preferably though not obligatorily at a speed of approximately rpm.

Said motor 40 is disposed so that its drive shaft, not shown, is disposed along a substantially vertical axis, with the center line M of the motor being offset from the center line S of the output shaft of the reducer, wherefor the motor is free to rotate about the output shaft center line (see FIG. 4).

It will be appreciated that the greater part of the torque created by the disc rotation is balanced by this off-center mounting of the right angle gear reducer motor.

The supporting of a great portion of the torque reaction by means of the unbalanced location of the driving motor thus permits the use of a flexible and sensitive spring to carry the balance of the torque.

The direction of rotation of the motor 40 will be understood to be clockwise, as viewed from the front as in FIG. 1.

The relationship of motor 40 and reducer 22 is thus such as to cause the weight of the motor to set up a moment of rotation in a clockwise direction.

The rotational movement of the disc 10 is such as to cause a certain amount of resistance and thereby the torque required to turn the disc is varied. It is this variation of torque which serves as a measure of the changes in consistency of the material passing through the regulator body.

A pair of horizontally-disposed lever arms 52 and 56 are each fixed to the body of the motor at a precise right angle to the vertically-disposed motor axis so that when the motor axis is vertical, the lever arms extend horizontally outwardly therefrom, one on either side of the motor.

The so-called left arm 52 at the left side of the motor, as viewed from the front in FIG. 1, is provided with a counterweight 60 which is threadedly receivable upon one end thereof and which may be locked in any desired position by means of a nut 62 or equivalent threaded upon the outer free end of said left arm 52. Said counterweight 60 is adapted for ready and precise manual adjustment along and relative to the left arm.

Said left arm 52 and associated counterweight 60 function to counterbalance partially the offset weight of motor 40 by providing a moment of rotation in a counterclockwise direction, as viewed from the front.

The so-called right arm 56 at the right side of the motor, as viewed from the front in FIG. 1, is connected to a motion transmitter 70, disposed vertically thereabove, by means of a connecting link 72 depending from member 70 and is connected by a link 74 to a compressible spring 76 for pulling said right arm 56 vertically downwardly in manner to set up an added moment of rotation in a clockwise direction, as viewed from the front, in the same direction as the moment of rotation set up by the unbalanced position of motor 40.

It is a salient feature of the invention that the sum of these two moments of rotation is preferentially balanced by the sum of the counter-clockwise moment of rotation caused by the counterweight and the torque developed by the disc rotation, all as will subsequently be more fully explained.

The motion transmitter 70 is a pnuematic instrument for translating the resultant movement of right arm 56 into a force of air pressure, which force may vary, for example, from between 3 psi. and p.s.i.

The motion transmitter 70 may be of the type disclosed in United States Letters Patent 2,298,112, granted Oct. 6, 1942, issued to Evan A. Edwards et al., and titled Regulator.

The arrangement therein shown included the case (herein shown by numeral 71) in combination with a vertically-disposed valve stem which is normally urged toward its uppermost position by a coil spring, the valve stem equivalent herein being represented by the connecting link 72.

Further in said patent, a fluid pressure actuated diaphragm motor operates to depress the valve stem against the coil spring action. This force finds its equivalent herein in the compressible spring 76.

The regulator of said patent is an element positioning arrangement and includes a control couple (a baffie and a nozzle) for positioning an element in response to changes in the space relation between the bafile and the nozzle, a source of pressure fluid flowing through the nozzle under the control of the bafi le, an expansible chamber re sponsive to the pressure of the fluid in the nozzle, means for moving one end of the baffie proportionately to the response of the chamber, a battle lever provided with means engaging the other end of the baffie, means for positioning one end of the bafile lever, and means responsive to the positioning of the element for adjusting the other end of the baflle lever.

Said motion transmitter 70 in the present invention is so related to the other instrumentalities hereof that for any given angular position of the right arm 56, there is a concomitant definite value of air pressure released by said motion transmitter in the form of an air signal which is transmitted through a pneumatic conduit 30 communicating at one end with said motion transmitter and communicating at its opposite end with a pneumatic controller 82.

Said pneumatic controller 82, upon sensing the air signal delivered thereto, effectuates an automatic adjustment of the quantity of dilution water added at a pump 86 disposed between a chest 88 and the regulator 12.

There is additionally a slight moment of rotation set up by the motion transmitter 70 which is in a counterclockwise direction and tends to oppose the moments set up by the motor and by the spring.

The mechanism is pre-set in the following manner with the motor axis M disposed vertically and with both the right and left arms 56 and 52 disposed horizontally, the length of the link 72, connecting the right arm 56 to the motion transmitter 70, is preset so that the signal sent to the pneumatic controller 82 is exactly at the midpoint of 9 p.s.i. and the controller is then pre-adjusted so that, with this value of a signal, a dilution valve 90 disposed between the controller 82 and the pump 86 remains in whatever position it may happen to be in.

Any subsequent increase in the value of the signal in actual operation will cause the dilution valve 98 to open wider and any decrease in the value of the signal will cause it to assume a smaller opening.

A pair of vertically-aligned adjustable stops 92 and 94 one above and one below the left arm, serve to limit the vertical movement of the left arm. They may be so adjusted that, with the left arm in its uppermost position (bearing agains the upper stop 92) and with the right arm in its lowermost position, the air signal delivered by the motion transmitter 70 is about 3 /2 p.s.i., and with the left arm in its lowermost position (bearing against the lower stop 94) the motion transmitter signal is approximately 14 /2 p.s.i.

Said stops 92 and 94 function to protect the motion transmitter 70 from damage through excessive movement. 1'

Having made these aforedescribed pre-setting ad ust- 6. ments, and with the motor running and the material passing from the chest 88 and through the pump as and the regulator body 12 at the desired consistency, the counterweight 60 is adjusted on the left arm 52 until the signal from the motion transmitter is exactly 9 p.s.i. No further adjustment is required.

If and when the consistency of the mass flowing through the body of the regulator increases, it will develop more torque. This, in turn, increases the moment of rotation in the counterclockwise direction, so that the right arm 56 rises so as to send a greater signal to the dilution valve wherefor the consistency is decreased. As soon as the consistency has been reduced to the desired control value, the torque returns to its former value and the motion transmitter 70 again sends a 9 p.s.i. signal to the controller 82.

As shown in FIG. 2, a pipe line 160 is provided which leads from the wall of the regulator to a meter 102 disposed in a purge water line 104. This forming no part of the invention, further discussion thereof will not be made.

A suitable air line 1% leads from the controller 82 to the dilution valve 90, while an air supply line 108 which leads into the dilution valve from an air supply source, not shown, controls the relative opening of said dilution valve.

A narrow bafile 110 will be observed to be fixed directly in front of the disc at the inlet side of the housing and horizontally through its entire diameter in manner to divert the stream lines of flow away from direct impingement against the rotating disc and provides an area of relatively quiet flow of material, but an area which is not stagnant as there will at all times be a change or movement of material directly adjacent the disc surface.

In the center of this baffle and therefore directly on the center line of the supply and discharge piping, a circular plate 112 is provided which is slightly smaller in diameter than the diameter of the supply and discharge piping.

Such circular plate and narrow baffle, being so located, serve effectively to separate and divide the entering stream of high velocity material into two diffused streams and at the same time to divert the entering stream from direct impingement against the surfaces of the torque disc.

The use of the baffle and circular diverting plate to effectively separate the high speed entering stream of pulp and to divert it outwardly toward the periphery of the cylindrical body 12 of the regulator prevents its direct impingement against the surfaces of the rotating disc 10 and thereby prevents erroneous torque readings which would otherwise be caused by changes in the rates at which material was being handled at various times.

Referring to FIG. 4 which is a diagrammatic representation of the disposition of forces, the weight of the motor is designated by the letter W, while the distance between the center lines S and M of the shaft and motor is represented by the letter D. The downward force exerted by the spring 76 is designated by F and the distance between the spring 76 and the center line S is designated by Y.

The weight of the counter weight 60 is represented by W, the distance from the counterweight to the center line S is represented by X, and the torque exerted by the disc 10 is represented by T.

Thus when the forces exerted on each side of the center line S are reduced to a formula, the following results:

As previously explained, the off-set position of the weight W of the motor relative to the centerline S is such that its moment which is of considerable magnitude in terms of inch-pounds, is clockwise as is also the comparatively small moment caused by the compression of the spring 75. These two clockwise moments are opposed by the sum of the counter-clockwise moments of the weight 60 and the torque T produced as the disc 10 is rotated.

For controlling in the lower ranges or spans of consistency, where the shear torque is small, the counterweight 60 is adjusted at some distance from the center line M of the motor to increase its effect. For the higher ranges of consistency, as the shear torque increases, the counterweight 68 is moved closer to said center line M. For the highest ranges of consistency, additional compression of the spring 76 may be required.

In the typical installation shown in FIG. 5, a mixture of pulp and water is fed from the chest 88 to the regulator 12 through the pump 36. Dilution water is fed into the system through an inlet disposed between the pump and the chest.

The controller 82 is interconnected to both the transmitter 70 and to the dilution valve 90.

Increases or decreases in the signal from the transmitter to the controller are transmitted to the dilution valve. An increase in the signal causes the valve to open wider and a decrease in the value of the signal causes it to assume a smaller opening, all so as to effectively control the consistency of the stock flowing to the regulator.

From the foregoing, it is obvious that I have provided. a truly novel consistency regulator.

It is believed that the gist of the invention will be clearly understood from the foregoing disclosure and ac cordingly, further analysis thereof at this point is considered unnecessary, as I have, in accordance with the provisions of the patent statutes, described the construction and principle of operation of my invention together with the apparatus which I believe to represent the best embodiment thereof, to the end that others can, by applying current knowledge, readily adapt it for various applications without omitting features which, from the standpoint of prior art, fairly constitute essential characteristics of its generic and/or specific aspects. The substitution of equivalents and other changes, modifications and alterations as circumstances may suggest or render expedient, are reasonably contemplated, the invention being susceptible of such without departing from its real spirit or underlying principles.

The protection which is sought for this invention is covered by the language of the above specification and the spirit represented thereby. It should be appreciated that its utility and application extend beyond the particular type of regulator illustrated and its broad scope and concept comprehend the useful and novel features set forth when combined with pulpers, machine chests and/or stock supply chests in a pulp delivery system.

The claims are desired to include within the scope thereof all of said suitable variations, modifications and equivalents by which substantially the results of the invention may be obtained through the use of substantially the same or equivalent devices or means. Accordingly, limitation hereof should only be made as determined by a proper interpretation of the prior art and the scope of the subjoined claims, in which it is my intention to claim all novelty inherent herein as broadly as possible.

I therefore particularly point out and distinctly claim as my invention:

1. For use in an apparatus for continuously controlling the consistency of a fluent material consisting of an admixture of solid matter and a freely-flowing liquid, a consistency responsive device comprising, a housing having aligned ingress and egress openings in spaced relation along the length thereof for the passage of the entirety of the fluent material lengthwise therethrough, a rotative torque generating sensing device positioned within the environment of the fluent material within the housing and being operative in a plane on the axis of flow of the fiuent material through the housing for producing a counterclockwise torque produced by the shear force as the sensing device is rotated clockwise and being responsive to changes in the shear force required to motivate the sensing device through the fluent material accordingly as its concentration is varied comprising: moment balancing means mounted relative to the housing for translating the responses to the changes in shear force and being inclusive of, a gear reducer motor pivotally mounted relative to the housing and having a horizontally-disposed output shaft extending into the housing and a drive shaft connected to said output shaft, said drive shaft being disposed along a substantially vertical axis with the vertical central axis of said drive shaft and motor being offset from the vertical central axis of said output shaft wherefore said motor is free to rotate about the axis of said output shaft, the sensing device being fixed to said output shaft and driven thereby at a constant speed rate, said motor being pivotally movable about said output shaft thereof to different offset positions according to changes in the required shear force allowing a clockwise moment of relatively great magnitude, a pair of torque arms fixed to said motor, one of said torque arms carrying a counter-weig'nt slidably adjustable to selected position therealong and allowing a counter clockwise moment for normally counteracting the torque required to rotate the sensing device, a compressible spring means, the other of said torque arms being linked to said spring means for allowing a relatively small clockwise moment upon compression of said spring means, the sum of the clockwise moments of the offset positioning of said motor and the compression of said spring means being opposed by the sum of the counterclockwise moment of the counterweight of the one of said torque arms and the torque produced by the shear of the rotating sensing device; a connecting link, the said other of said torque arms being mechanically interconnected to said connecting link.

2. The sensing device as set forth in claim 1, including a narrow baflle disposed across the entire cross section of the housing and in the same plane as said responsive device and immediately in advance thereof for deflecting the stream lines of the moving fluent material from direct impingement against said responsive device.

References Cited in the file of this patent UNITED STATES PATENTS 1,888,431 Osbourne Nov. 22, 1932 2,242,419 Cowles May 20, 1941 2,339,991 Hagy Jan. 25, 1944 2,354,299 Bays July 25, 1944 2,519,378 Kilpatrick Aug. 22, 1950 2,846,873 Kalle Aug. 12, 1958 2,974,524 Loska Mar. 14, 1961 3,027,526 Head Apr. 3, 1962 FOREIGN PATENTS 468,041 Great Britain July 30, 1936 618,687 Canada Apr. 18, 1961 

1. FOR USE IN AN APPARATUS FOR CONTINUOUSLY CONTROLLING THE CONSISTENCY OF A FLUENT MATERIAL CONSISTING OF AN ADMIXTURE OF SOLID MATTER AND A FREELY-FLOWING LIQUID, A CONSISTENCY RESPONSIVE DEVICE COMPRISING, A HOUSING HAVING ALIGNED INGRESS AND EGRESS OPENINGS IN SPACED RELATION ALONG THE LENGTH THEREOF FOR THE PASSAGE OF THE ENTIRETY OF THE FLUENT MATERIAL LENGTHWISE THERETHROUGH, A ROTATIVE TORQUE GENERATING SENSING DEVICE POSITIONED WITHIN THE ENVIRONMENT OF THE FLUENT MATERIAL WITHIN THE HOUSING AND BEING OPERATIVE IN A PLANE ON THE AXIS OF FLOW OF THE FLUENT MATERIAL THROUGH THE HOUSING FOR PRODUCING A COUNTERCLOCKWISE TORQUE PRODUCED BY THE SHEAR FORCE AS THE SENSING DEVICE IS ROTATED CLOCKWISE AND BEING RESPONSIVE TO CHANGES IN THE SHEAR FORCE REQUIRED TO MOTIVATE THE SENSING DEVICE THROUGH THE FLUENT MATERIAL ACCORDINGLY AS ITS CONCENTRATION IS VARIED COMPRISING: MOMENT BALANCING MEANS MOUNTED RELATIVE TO THE HOUSING FOR TRANSLATING THE RESPONSES TO THE CHANGES IN SHEAR FORCE AND BEING INCLUSIVE OF, A GEAR REDUCER MOTOR PIVOTALLY MOUNTED RELATIVE TO THE HOUSING AND HAVING A HORIZONTALLY-DISPOSED OUTPUT SHAFT EXTENDING INTO THE HOUSING AND A DRIVE SHAFT CONNECTED TO SAID OUTPUT SHAFT, SAID DRIVE SHAFT BEING DISPOSED ALONG A SUBSTANTIALLY VERTICAL AXIS WITH THE VERTICAL CENTRAL AXIS OF SAID DRIVE SHAFT AND MOTOR BEING OFFSET FROM THE VERTICAL CENTRAL AXIS OF SAID OUTPUT SHAFT WHEREFORE SAID MOTOR IS FREE TO ROTATE ABOUT THE AXIS OF SAID OUTPUT SHAFT, THE SENSING DEVICE BEING FIXED TO SAID OUTPUT SHAFT AND DRIVEN THEREBY AT A CONSTANT SPEED RATE, SAID MOTOR BEING PIVOTALLY MOVABLE ABOUT SAID OUTPUT SHAFT THEREOF TO DIFFERENT OFFSET POSITIONS ACCORDING TO CHANGES IN THE REQUIRED SHEAR FORCE ALLOWING A CLOCKWISE MOMENT OF RELATIVELY GREAT MAGNITUDE, A PAIR OF TORQUE ARMS FIXED TO SAID MOTOR, ONE OF SAID TORQUE ARMS CARRYING A COUNTER-WEIGHT SLIDABLY ADJUSTABLE TO SELECTED POSITION THEREALONG AND ALLOWING A COUNTER CLOCKWISE MOMENT FOR NORMALLY COUNTERACTING THE TORQUE REQUIRED TO ROTATE THE SENSING DEVICE, A COMPRESSIBLE SPRING MEANS, THE OTHER OF SAID TORQUE ARMS BEING LINKED TO SAID SPRING MEANS FOR ALLOWING A RELATIVELY SMALL CLOCKWISE MOMENT UPON COMPRESSION OF SAID SPRING MEANS, THE SUM OF THE CLOCKWISE MOMENTS OF THE OFFSET POSITIONING OF SAID MOTOR AND THE COMPRESSION OF SAID SPRING MEANS BEING OPPOSED BY THE SUM OF THE COUNTERCLOCKWISE MOMENT OF THE COUNTERWEIGHT OF THE ONE OF SAID TORQUE ARMS AND THE TORQUE PRODUCED BY THE SHEAR OF THE ROTATING SENSING DEVICE; A CONNECTING LINK, THE SAID OTHER OF SAID TORQUE ARMS BEING MECHANICALLY INTERCONNECTED TO SAID CONNECTING LINK. 